The avowed purpose of alliances is to provide for national defense.However, entangling alliances led to a world war in 1914.
Could alliances threaten rather than reassure? Might current alliances possibly lead to war rather than prevent it? Explain your answer.
I think that the question raised is a good one. I would point out that one lesson that can be learned from the alliance system conceived at the outset of the First World War is that modern alliances should try to be as open and as transparent as possible while being flexible and representative of a good relationship. The challenges in the First World War setting were that alliances were secretly forged between nations and were completely binding. When one nation declared war on another, they had no idea who else was being brought into the conflict via secret alliance. Knowing this in the open might have allowed more diplomatic channels to be pursued with more vigor. Additionally, the alliance system was so binding that when one nation was threat end, its allies had to plunge their own nations into war in honor of the alliance. A modern alliance can be more pliable, and can feature some level of articulation where an ally can suggest not to go to war, and to seek another remedy or the alliance is dissolved. I think that modern alliances can gain much from the lessons of those forged at the outset of the First World War.
International relations theorists call this the "security dilemma." It is the idea that things that a country does to make itself secure really make it less secure. Country A acts to protect itself (say by making an alliance) but Country B thinks that the alliance is meant to harm it and it becomes more likely to attack Country A. So definitely yes -- this can happen.
I do not really think that current alliances are likely to lead to war. I think current alliances are much looser than previous ones, mostly because there is no major threat to the larger countries of the world. The US is not afraid of Russia, for example, and is not likely to be pulled into war because of its NATO alliances with Eastern European countries.